Re: AC_PROG_CC fails when target C library is missing fopen

[Ralf Corsepius]

On 08/12/2009 06:51 PM, Ralf Corsepius wrote:
> On 08/12/2009 02:09 PM, Eric Blake wrote:
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA1
> >
> > According to Paolo Bonzini on 8/10/2009 4:27 PM:
> > > On 08/11/2009 12:11 AM, Ralf Wildenhues wrote:
> > > > I don't see in this discussion where the main argument to switch to
> > > > using fopen is addressed:
> > > > <http://thread.gmane.org/gmane.comp.sysutils.autoconf.patches/6656>
> > > > IOW, how do you prevent AC_COMPUTE_INT and friends from getting you
> > > > wrong answers on your system (if you happen to have a simulator
> > > > around)?
> > > In my patch I use an empty source code file to determine the default
> > > file name. Then I use one with fopen to determine if the user is
> > > cross-compiling; this would fail for RTEMS so that the preprocessor-only
> > > AC_COMPUTE_INT is used.
> > If we get feedback from both RTEMS

I am observing what I would call "partial success".

Using atoi definitely is much better than fopen for RTEMS
(Thanks Paolo!).



However, with this check applied, I am now observing a similar problem 
with autoconf's "check for cross-compilation", when using a toolchain 
with RTEMS function stubs removed (The official rtems toolchains have 
these stubs)

Example:

# cat configure.ac
AC_PREQ([2.64])
AC_INIT([cccheck],[0.2])
AM_INIT_AUTOMAKE([foreign 1.11 dist-bzip2])
AC_PROG_CC
AC_CONFIG_FILES(Makefile)
AC_OUTPUT

# ./configure --host=i386-rtems4.10

The resulting config.log shows this:
...
configure:2729: checking whether we are cross compiling
configure:2737: i386-rtems4.10-gcc -o conftest    conftest.c  >&5
/opt/rtems-4.10/lib64/gcc/i386-rtems4.10/4.4.1/../../../../i386-rtems4.10/lib/libc.a(lib_a-findfp.o): 
In function `__sfmoreglue':
/users/rtems/src/rpms/BUILD/rtems-4.10-i386-rtems4.10-gcc-4.4.1/build/i386-rtems4.10/newlib/libc/stdio/../../../../../gcc-4.4.1/newlib/libc/stdio/findfp.c:88: 
undefined reference to `_malloc_r'
/opt/rtems-4.10/lib64/gcc/i386-rtems4.10/4.4.1/../../../../i386-rtems4.10/lib/libc.a(lib_a-fopen.o): 
In function `_fopen_r':
/users/rtems/src/rpms/BUILD/rtems-4.10-i386-rtems4.10-gcc-4.4.1/build/i386-rtems4.10/newlib/libc/stdio/../../../../../gcc-4.4.1/newlib/libc/stdio/fopen.c:141: 
undefined reference to `_open_r'
/opt/rtems-4.10/lib64/gcc/i386-rtems4.10/4.4.1/../../../../i386-rtems4.10/lib/libc.a(lib_a-fseek.o): 
In function `_fseek_r':
/users/rtems/src/rpms/BUILD/rtems-4.10-i386-rtems4.10-gcc-4.4.1/build/i386-rtems4.10/newlib/libc/stdio/../../../../../gcc-4.4.1/newlib/libc/stdio/fseek.c:233: 
undefined reference to `_fstat_r'
/users/rtems/src/rpms/BUILD/rtems-4.10-i386-rtems4.10-gcc-4.4.1/build/i386-rtems4.10/newlib/libc/stdio/../../../../../gcc-4.4.1/newlib/libc/stdio/fseek.c:258: 
undefined reference to `_fstat_r'
/opt/rtems-4.10/lib64/gcc/i386-rtems4.10/4.4.1/../../../../i386-rtems4.10/lib/libc.a(lib_a-makebuf.o): 
In function `__smakebuf_r':
/users/rtems/src/rpms/BUILD/rtems-4.10-i386-rtems4.10-gcc-4.4.1/build/i386-rtems4.10/newlib/libc/stdio/../../../../../gcc-4.4.1/newlib/libc/stdio/makebuf.c:59: 
undefined reference to `_fstat_r'
/users/rtems/src/rpms/BUILD/rtems-4.10-i386-rtems4.10-gcc-4.4.1/build/i386-rtems4.10/newlib/libc/stdio/../../../../../gcc-4.4.1/newlib/libc/stdio/makebuf.c:95: 
undefined reference to `_malloc_r'
/users/rtems/src/rpms/BUILD/rtems-4.10-i386-rtems4.10-gcc-4.4.1/build/i386-rtems4.10/newlib/libc/stdio/../../../../../gcc-4.4.1/newlib/libc/stdio/makebuf.c:110: 
undefined reference to `_isatty_r'
/opt/rtems-4.10/lib64/gcc/i386-rtems4.10/4.4.1/../../../../i386-rtems4.10/lib/libc.a(lib_a-stdio.o): 
In function `__sclose':
/users/rtems/src/rpms/BUILD/rtems-4.10-i386-rtems4.10-gcc-4.4.1/build/i386-rtems4.10/newlib/libc/stdio/../../../../../gcc-4.4.1/newlib/libc/stdio/stdio.c:124: 
undefined reference to `_close_r'
/opt/rtems-4.10/lib64/gcc/i386-rtems4.10/4.4.1/../../../../i386-rtems4.10/lib/libc.a(lib_a-stdio.o): 
In function `__swrite':
/users/rtems/src/rpms/BUILD/rtems-4.10-i386-rtems4.10-gcc-4.4.1/build/i386-rtems4.10/newlib/libc/stdio/../../../../../gcc-4.4.1/newlib/libc/stdio/stdio.c:86: 
undefined reference to `_write_r'
collect2: ld returned 1 exit status

I.e. something still pulls in symbols, RTEMS libc (newlib) doesn't 
contain. We still needs stub functions in libc/newlib to let AC_PROG_CC 
work out correctly.

Ralf